3. A shot fired suspended in a case into which gas was conducted, and
the atmospheric air allowed to enter so as to form an explosive
mixture. The gas was not fired.

4. A shot fired in a boiler flue 16 ft. by 2 ft. 8 in., placed
horizontally, in which was a quantity of fine coal dust kept suspended
in the air by the action of a fan. No flame nor ignition of the coal
dust took place.

5. A shot fired as above, except that an explosive mixture of gas and
air was flowing into the boiler tube in addition to the coal dust.
That this mixture was firedamp was proved by the introduction of a
safety lamp, the flame of which was elongated, showing what miners
call the "blue cap." There was no explosion of the gas or sign of
flames.

6. A shot of roburite fired in the boiler tube without any gas or
suspended coal dust. The report was quite as loud as in the preceding
case; indeed, to several present it seemed more distinct.

7. A shot of ½ lb. gunpowder was fired under the same condition as No.
5, i.e., in an explosive mixture of gas and air with coal dust. The
result was most striking, and appeared to carry conviction of the
great comparative safety of roburite to all present. Not only was
there an unmistakable explosion of the firedamp, with very loud
report, and a vivid sheet of flame, but the gas flowing into the far
end of the boiler tube was ignited and remained burning until turned
off.

_In the Pit._--1. A 2 in. hole was drilled 4 ft. 6 in. deep into coal,